Devices used to participate in video conferences may experience fluctuations in available bandwidth. This could adversely affect the quality of a user's video conference experience by reducing the quality of signals received by a video conference device from other devices participating in the call. For instance, at one moment the channel between the endpoints in the conference may accommodate the transmit bit rate of a first video conference device. Subsequently however the bandwidth of the channel may drop. In this situation the transmit bit rate of the first device may exceed the maximum bit rate of the channel. This would have the result that not all packets transmitted from the first video conference device are received by the second video conference device, thereby reducing the quality of the video conference experience of a user of the second device. Setting low bit rates for communication reduces the chances of lost packets but results in video in a lower quality than could be accommodated by the channel.
Dynamic bandwidth adaptation techniques have been used which reduce the effects of bandwidth fluctuations experienced during video conference calls. Such techniques involve changing the transmit bit rate of one video conference device on-the-fly in accordance with the receive bit rate of another video conference device.
The problem still exists however that the initial transmit bit rate during a video conference call may exceed the initial bit rate that the channel between the endpoints can accommodate, or that it can be significantly lower than the bit rate that the channel can accommodate. Although dynamic bandwidth adaptation techniques may be used to adjust the transmit bit rate to accommodate the maximum receive bit rate, while this is taking place the quality of the video conference experience may be reduced due to packet loss or due to underutilisation of the channel bandwidth. Aspects of the present invention have been conceived with this in mind.